Biomechanical Characteristics of Lumbar Fusion by Three Internal Fixation Methods / 医用生物力学

Objective To analyze the biomechanical characteristics of lumbar fusion by 3 internal fixation methods using three-dimensional (3D) finite element (FE) method. Methods The FE fixation models of physiological L4-5, unfixed fusion L4-5, translaminar facet screw (TLFS), lumbar pedical screw+translaminar facet screw (LPS+TLFS), bilateral pedical screw (BPS) with complete osteotomy or partial osteotomy of facet joint were established, respectively. The biomechanical characteristics of L4 centrum and implants under six motion states (spinal flexion, extension, lateral bending and axial rotation) in L4-5 fusion model and three fixation models were compared by FE analysis. Results The average maximal displacements of L4 centrum in L4-5 unfixed fusion model, TLFS model, TLFS+LPS model, BPS model were 1.410 8, 0.629 8, 0.336 9, 0.252 8 mm (complete osteotomy of facet joint) and 1.296 7, 0.844 9, 0.340 9, 0.273 8 mm (partial osteotomy of facet joint); the average maximal displacements of cage were 0.479 9, 0.319 5, 0.167 6, 0.126 4 mm (complete osteotomy of facet joint) and 0.378 7, 0.348 4, 0.183 5, 0.137 2 mm (partial osteotomy of facet joint)；the average maximum stresses of screws and rods during 6 motions in TLFS model, TLFS+LPS model, BPS model were 178.34, 79.55, 56.33 MPa (complete osteotomy of facet joint) and 142.29, 103.02, 59.69 MPa (partial osteotomy of facet joint). Conclusions In percutaneous transforaminal lumbar interbody fusion, the fixation effect of BPS model was similar to that of LPS+TLFS model. BPS model could achieve the best spinal stability, and LPS+TLFS model was also a good fixation method. The stability of TLFS model alone was relatively poor, but it was still better than that of cage bone graft without internal fixation. In the absence of internal fixation, preservation of the articular process significantly increased stability of the spine.

Biomechanical characteristics of transforaminal lumbar interbody fusion combined with different pedicle screw fixation methods in single-segment lumbar spine and adjacent segments / 中国组织工程研究

BACKGROUND: Decompression-fixation-fusion is the key to spinal surgery since early effective fixation to achieve intervertebral fusion can restore spinal stability in lumbar degenerative disease. OBJECTIVE: To compare biomechanical stability of fusion segment and adjacent segments of bilateral pedicle screw fixation, unilateral pedicle screw fixation and unilateral pedicle screw combined with contralateral translaminar facet screw fixation under transforaminal lumbar interbody fusion. METHODS: Eighteen fresh calf L3-5 specimens were selected. Different forms of fixation were conducted under transforaminal lumbar interbody fusion. The specimens were divided into group A (complete specimens) and group B (bilateral pedicle screws), group C (unilateral pedicle screws), and group D (unilateral pedicle screw combined with contralateral translaminar facet screw). The range of motion of adjacent segment L3-4 and fusion segment L4-5 in six directions of backward extension, forward bending, left bending, right bending, left rotation and right rotation and the stiffness of fusion segment L4-5 were tested. RESULTS AND CONCLUSION: (1) For the range of motion of fusion segment L4-5, the stability was highest in the group B in six directions, followed by group D, which showed similar results in rotation in the group B (P > 0.05). The stability of right curvature and left rotation in group C was insufficient, and there was no significant difference in range of motion between group A and group C (P > 0.05). The range of motion in group A was largest and the stability was worst in the six motion directions. (2) For the stiffness value of fusion segment L4-5, the stiffness value of group B was largest in six directions, which was significantly different from other groups (P 0.05). There was no significant difference between group C and group A in the range of motion of six directions (P > 0.05). (4) The results showed that the motion ramge of unilateral pedicle screw fixation in the right and left rotation directions was large in the early stage, which was close to that of the complete specimen group. There is a shortage of stability, so we need to use it carefully and grasp the indications strictly. Unilateral pedicle screw fixation combined with contralateral translaminar facet screw fixation improves the disadvantages of asymmetric fixation of unilateral pedicle screw, increases the stability of rotation and lateral bending, and avoids the influence of bilateral pedicle screw fixation on adjacent segments, thus becoming an effective clinical surgical treatment.

Case control study on two different surgical approaches combined fixation with lumbar interbody fusion for the treatment of single segmental lumbar vertebra diseases / 中国骨伤

<p><b>OBJECTIVE</b>To discuss the advantages and disadvantages of two different surgical approaches combined fixation with lumbar interbody fusion in treating single segmental lumbar vertebra diseases.</p><p><b>METHODS</b>The clinical data of 86 patients with single segmental lumbar vertebra diseases treated from June 2011 to June 2013 was retrospectively analyzed. There were 33 males and 53 females, aged from 28 to 76 years old with an average of 53.0 years. Among them, there were 39 cases of lumbar disc degeneration, 22 cases of lumbar disc herniation complicated with spinal canal stenosis, 9 cases of huge lumbar disc herniation and 16 cases of lumbar degenerative spondylolisthesis (Meyerding degree I ). Lesion sites contained L3, 4 in 5 cases, L4, 5 in 70 cases and L5S1 in 11 cases. All the patients were treated with internal fixation and lumbar interbody fusion with 45 cases by midline incision approach (median incision group) and the other 41 cases by channel-assisted by muscle-splitting approach(channel group). Incision length, operation time, intraoperative bleeding and postoperative drainage were recorded in two groups. Visual analogue scale(VAS) was used to assess lumbar incision pain 72 h after operation. Depended on imaging results to compare the changes of the disc space height in lesion in preoperative, postoperative and final follow-up, the coronal and sagittal Cobb angle in preoperative and final follow-up, the area of multifidus and the degree of multifidus fat deposition before and after operation between two groups. Loosening or fragmentation of internal fixation, displacement of intervertebral cage and interbody fusion were observed in each group. Japanese Orthopedic Association (JOA) scoring system was used to evaluate the function before operation and at the final follow-up.</p><p><b>RESULTS</b>The channel group was superior to the median incision group in incision length and postoperative drainage while the median incision group was less than the channel group in the operation time and intraoperative bleeding. The average VAS score of lumbar incision 72 h after operation was 1.50 points in median incision group and 0.97 points in channel group, and there was significant difference between two groups(<0.05). No incision infection was found, but there were 4 cases of incisional epidermal necrosis, 1 case of incision healed badness, and 3 cases of nerve injury in channel group. The incidence of cacothesis of pedicle screw were 5.0% and 3.6% in median incision group and channel group respectively, and there was no significant difference between two groups(>0.05). The incidence of cacothesis of translaminar facet screw were 6.6% and 12.2% in median incision group and channel group respectively, and there was significant difference between two groups(<0.05). All the patients were followed up for 12 to 36 months with a mean of 22.8 months. The changes of disc space height had statistical difference between preoperative and postoperative(<0.05) in all patients, but there was no significant difference between postoperative and final follow-up(>0.05), however, there was no significant difference 3 days after operation and final follow-up between two groups(>0.05). At final follow-up, coronal and sagittal Cobb angle were obviously improved in all patients(<0.05), but there was no significant difference between two groups(>0.05). One year after operation, the area of multifidus in median incision group was (789.00±143.15) mm² less than preoperative(1 066.00±173.55) mm² (<0.05), and in channel group, was(992.00±156.75) mm² at 1 year after operation and(1 063.00±172.13) mm² preoperatively, there was no significant difference between them(>0.05), however, there was significant difference one year after operation between two groups (<0.05) . About the degree of multifidus fat deposition, there was significant difference between one year after operation and preoperation in median incision group (<0.05), but there was no significant difference between one year after operation and preoperation in channel group (>0.05), and there was significant difference at one year after operation between two groups(<0.05). During the follow-up period, neither pedicle screw and/or translaminar facet screw loosening, displacement or fragmentation nor displacement of intervertebral cage were found. The lumbar interbody fusion rate was 95.6% in median incision group and was 95.1% in channel group, and there was no significant difference between two groups(>0.05). No obvious adjacent segmental degeneration was observed in fixed position. JOA score in median incision group was significantly increased from 8-16 points (average: 12.77±2.56) preoperative to 21-29 points (average: 25.20±2.43) at final follow-up(<0.05); and in channel group was significantly increased from 8-16 points (average: 12.64±2.37) preoperative to 23-29 points(average: 26.7±1.82) at final follow-up(<0.05); there was also significant difference between two groups at final follow-up.</p><p><b>CONCLUSIONS</b>Compared to the median incision approach, unilateral pedicle screw combined with contralateral translaminar facet screw fixation using channel-assisted by muscle-splitting approach has advantages of small incision, less trauma, fast recovery and so on. However, it also has shortages such as high surgical complications incidence, especially in cases that.</p>

Posterior Lumbar Intebody Fusion with Unilateral Transpedicular Screw and Contralateral Translaminar Facet Screw Fixation in Lumbar Spinal Stenosis / 대한척추외과학회지

STUDY DESIGN: A retrospective study. OBJECTIVES: To describe the surgical procedure and assess the results of an unilateral transpedicular screw and contralateral translaminar facet screw fixation in degenerative lumbar stenosis. SUMMARY OF LITERATURE REVIEW: A drawback of conventional lumbar fusion is the extensive soft-tissue destruction that is essential when inserting a screw and preparing the fusion bed. The development of a procedure that minimizes the tissue trauma without compromising the effectiveness of the conventional posterior lumbar interbody fusion (PLIF) should be pursued in lumbar spinal stenosis. MATERIALS AND METHODS: From August 2004 to November 2005, PLIF was performed on 25 consecutive patients who had lumbar spinal stenosis. Among them, 10 patients underwent with unilateral transpedicular screw and contralateral translaminar facet screw fixation (Group 1), and 15 patients underwent traditional bilateral transpedicular screw fixation (Group 2). The clinical and radiological results in the two groups were compared. RESULTS: The mean follow-up was 17.6 and 20.5 months in Groups 1 and 2, respectively. Group 1 had less blood loss, fewer transfusion requirements (P.0.05) in the surgical procedure, and less postoperative back pain (P.0.05). There was no significant difference between the two groups in the clinical results such as the VAS score for back pain and the Kirkadly-Willis criteria at the last follow-up, and the radiological results such as the changes in the disc height and interbody fusion. CONCLUSION: The PLIF with unilateral transpedicular screw and contralateral translaminar facet screw fixation in lumbar spinal stenosis has advantages over conventional PLIF of less soft tissue injury, and produces good clinical results.

Experimental research on biomechanical stability about L_5S_1 ALIF / 中国矫形外科杂志

[Objective] To evaluate the biomechanical stability of lumbar intact specimen,anterior lumbar interbody fixation(ALIF)specimen,ALIF specimen fixed with pedicle screw and ALIF specimen fixed with translaminar facets screw.[Method]Each of eight adult fresh cadaver specimen of lumbarsacral segmcnts was analyzed in four states(groups):intact,L5S1 ALIF,L5S1 ALIF fixed with pedicle screw or fixed with translaminar facets screw,test and compare its range of motion(ROM)in flexion,extension,lateral bending and axial rotation.[Result]The ROM of ALIF specimen in extension was larger than that of intact specimen(P

Placement of percutaneous translaminar facet screw: an anatomic study / 中国矫形外科杂志

[Objective]To provide anatomic basement for the clinic appliance of percutaneous thranslaminar facet screw.[Method]From L_1 to L_5,anatomic measurements for screw path length,superior and inferior lamina border thickness in 30 dried lumbar spines,caudal and lateral angles of laminar were measured with CT and X ray.[Result]The superior border of the lamina was relatively thinner from L_1 to L_5,The thickness of the inferior border of the lamina,the mean values of the length of the screw path and lateral angle gradually increased,and the caudal angle of screw placement relative to transverse plane gradually decreased.[Conclusion]A translaminar facet screw with 4.5 mm in diameter is safe.from L_(1~5).Screw should be inserted in inferior lamina border,not in the superior border of the lamina,caudal and lateral angles of laminar should be ajustable to fit the lumbar facet joint.